1. Field of the Invention
The invention relates to thread handling devices for use in a sewing machine, and more particularly to mechanism for pulling thread from a bobbin spool in a lock stitch sewing machine.
2. Description of the Prior Art
It is known to provide a lock stitch sewing machine with means for pulling thread from a bobbin spool for use in the formation of stitches, and it is usual for such thread pulling means to supply a constant amount of thread for each stitch regardless of the material being sewn, the length of stitch called for, or the type of stitch being formed. However, the feeding of constant amounts of bobbin thread regardless of sewing conditions is a disadvantage in that it may result in stitches (straight or zigzag) which are drawn too tight and cause puckering of material being sewn, or in stitches which are inadequately locked and may therefore easily pull out of the material.